Damping magnet system



Jan' 126, 1943. A. R. NOBBS 2,309,414

DAMPING MAGNET SYSTEM Filed April 30, 1940 Ja //v-g 27 1 N NEGATNE TEMPERATURE CoeFFncnEN'r oF PeRMEABiLlTY. Z7 22 29 NoN- MAGNETlc SPACER.

, inventori. Mbert F?. Nobbs,

by wwf 2M H15 Attorn ey. f

Patented Jan. 26, 1943 DALIPING MAGNET SYSTEBE ruben n, Nubia, Peterborough, ontario, omda, asslg'nor to General Electric Company. a corporation of New York Application April '30, 1940, Serial No. 332,505

Canada October 24, 1939 s claims. (ci. r11-264)' My invention relates to electric meters of the induction disc type, and more particularly to damping apparatus therefor.

Induction disc meters comprise a rotatable conducting disc and an electromagnetic driving system energized from the source of power to be measured acting thereon whereby the amount of rotation of the disc is utilized to give a measaiI ure of the power consumed in the circuit. It' is customary to provide a damping apparatus comprising a permanent magnet coop'erating with the disc to provide a drag thereon and stabilize the operation.

It is an object of my invention to provide a damping magnet which shall be compact in structure, veconomical in manufacture, and satisfactory in operation.

The speed of rotation of an induction meter disc has a tendency to vary with the temperature of the meter, to run faster as the temperature rises. It has been proposed to correct this temperature error by applying to the damping magnet structure a xed shunt of material having a negative temperature coeillcient of permel ability whereby the drag of the magnet is increased with rising temperature and compensates for the tendency to run too fast. It is an object of my invention to incorporate such a temperature compensation device in my damping magnet in a simple, eifective and novel manner.

It is customary to calibrate induction disc meters by varying the effectiveness of the damping magnet on the disc. One manner in which this has been accomplished is to mount a piece of soft iron adjacent the magnet poles and provide means whereby the piece may be adjusted in position with respect to the poles, whereby a greater or less amount of the permanent magnet flux is diverted from the magnetic path acting on the disc. It is an object ofmy invention to provide such a compensating shunt as a part of my damping magnet structure in such a manner as to provide a simple, compact and effective unit which will provide straight line adjustment.

The objects and advantages of my invention will be more completely appreciated from a consideration of the following detailed description taken in connection with the drawing, in which the same reference characters refer tothe same parts throughout the several views, and yin which:

Figurel is a general view of an induction meter with the damping magnet apparatus of my invention located in operative position;

Figure 2 is an end view of my damping mag- 'E net apparatus, looking from the right of Fig. 1 towards. the axis of the disc;

Figure 3 is an end view from the opposite end from F18. 2;

Figure 4 is a central, longitudinal, cross-sectional view on the line 4--4 of Figures 2 and 3;

Figure 5 is a perspective view of the magnet; and

Figure 6 is a perspective view of a spacer employed.

Referring to the drawing, and particularly Figure 1, reference character I0 represents a metal framework on which the operating parts of the meter are mounted. Certain parts, including an electromagnetic driving system for the disc, are mounted on the frame i0 and are enclosed within a metal housing Il secured to the frame I0 in the customary manner. These parts are not shown, as they form in themselves no part of my present invention. A spindle I2 is mounted on brackets i3 and i4 and this spindle carries a thin disc i5 of conducting material, such as aluminum. The disc i5 extends into the casing Il in cooperating relation with an electromagnetic driving system. Rotation of the disc by the driving system actuates a reg ister, generally shown at I6.

The damping magnet apparatus of my invention, generally indicated by the reference character I1, is detachably mounted in a denite position on a bracket I8 extending from the frame I0. The customary removable glass cover I8 is shown in dotted lines.

The damping magnet consists of a pair of blocks of magnetic ,material 20, mounted for example by means of rivets 2| at the inside of one arm 22 of a U-shaped yoke of cold rolled steel and spaced apart laterallyalong the vedge of the arm approximately equidistant from the neck 25 of the yoke. The other ends ofthe magnets extend close to the other arm 23 of the yoke so that when the structure is mounted on the bracket i8, as indicated in Fig. 1, the disc I5 is centrally located 'in the gap between the permanent magnet blocks 20 and the leg 23 of The yoke arms 22 and 23 extend radially inward with respect to the meter disk i6 and the neck 25 of the yoke is radially outward. The pair of magnets are mounted with their ends of opposite polarity in contact with the arm 22 and their polarity is indicated in Fig. 3. The magnetic circuit is indicated by the dotted line 24. It will be observed that the linesbf ux extend across the gap in which the disc is located from one magnet to one end of the armature constituted by the leg 23 of the yoke and then from the other end of the armature 23 across the air gap to the other magnet. The magnetic circuit is completed at the lower end of the magnet by the lower leg 22 of the bracket.

The permanent magnets 20 are relatively short in comparison with their cross-sectional area and the length of the air gaps and are composed of a high coercive force material, such for example as is available under the trade name nica The high coercive force permanent magnet material is not of itself of my invention. if. suitable material is that described in Patent No. 2,027,996, Mishima, or that described in Fatent 1,968,539, Ruder.

'The yolre, for convenience in manufacture, is up oi of sections, a dat section forming the leg .i, to iv `lich the magnets 20 are secured, and an L-shaped section, which is secured thereto in stepped relation as indicated at 26.

For meter temperature compensation, a strip 'i oi material having a negative temperature coerlicient oi permeability is Welded to that side of the pair oi magnets facing the neck 25 oi the yoke. .A portion of the iiux ci the magnets i@ will be shunted through the strip 21. With a rise in temperature, a lesser amount of flux :t diverted through the shunt, and consequently greater amount oi nur: exists across the gap and is available iol' damping the disc.

The calibrating adjustment is provided by the adjustable shunt 2S which is mounted in the space between the permanent magnets 20 and is provided with an adjusting arrangement Whereby it may be moved into and out of the space. ils it is moved into or out of the space between the magnets, a greater or a lesser amount of the available magnet flux is diverted from the air gaps. rihe entering face of the shunt 2B is bevelled, as shown at 28, so that the increase in effectiveness oi the shunt is gradual as it enters between the magnets in such a manner tha straight line adjustment curve is provided; that is, for equal amounts of rotation of the adjust head to be presently described, equal amoun of chanffe of speed oi the meter disc will l e tained. The adjusting mechanism consist threaded bolt 3l! of brass or other nomme material cooperating with a threaded h. the shunt 2S and having an adjusting mounted centrally oi the neck of the yolzc. adjusting head 3i is rabbeted, whereby c. sho

L'. O t

yolte and the bolt is biased with the against the neck oi the yoke by means r spi" -e f rel hairpin conngura the space between the i l. That section o. s spring 33 may be reduc commodate the spring.

F oi' the boit 3S, who

entering edge proximetely speed oi the me calibration oi t" i -magnetic is' inserted echanically space t` The bolt Si passes iovided in th space; 3i,

eter.

the lower ntegral Wfth U the material of the yoke and :formed ation of punching out the windev It will be apparent from 5 that I have provided a magia small and compact v.. cost of manufacture. calibration adjust: pensation are all combi uniform temperatur and removal and the meter can be h bration. Straight without the nec testing of the the pointer in [ne with the marie: coercive force e .iescription mbly which is have e low d` fnping magnet,

ierfiture comone unit. Thus, "a ion is obtained '1 griet fiori he caliobtained ct and he use of -n conjunction the disc. High in of a type which substantially unity of the 20 damping syst ^'i stray fields is used.

I have 'Jribed in detail a but it will art that many possible and I modifications ope oi my in- ,ended claims. o secure by specific e be obvious to i COE CNH,

er pole faces "Ween a pair se is adapted shunt of ccupying the l.ounted for face of the icrease in efde u straight iprocation therein,

v.cunt being beveled for veness of the n' adjustment cur A damping magnet for rotating disc devices accordance with l, in which temperature ompensation for said devices is provided by a tively flat strip of material having a negave temperature coefficient permeability ich extends along and it to substanr coplansr side surfaces or pair of magts as a shunt.

A damping magnet for a rotating disk decomprising a pair oi reiativ y short permanent magnets of high coercive force material and spaced apart on a strip of highly permeable material with poles of opposite p0- iarity ir; Contact with the an armature o! material of high permeability spaced from the other pole face of the sa aguets to form therebetween a pair oi' air gaps in which a rotatable disk. is adapted to mo a ealibrating adjustment shunt of material oi' relatively high permeability occupying the ce between said ocation therein, iol interposed beent shunt and d magnets ior from said ceci . ijacent side Sfid 

